Yesterday’s men’s 15km freestyle interval start race featured one of the most split fields we’ve seen in that event in a long time. The top three, Northug, Olsson and Gjerdalen had modest gaps between them, but then there was just over 30 seconds back to 4th place.
How big was this gap between the podium and 4th? It was the biggest in history (post-1992):
These are the gaps in median percent back between 3rd and 4th in every men’s 10/15km interval start WC, WSC, OWG or TdS race since 1992. I’ve separated the classic/freestyle races, as well as the WSC/OWG (Championships) and regular World Cups. Yesterday’s race was a bit of an outlier, as you can see.
However, it was only this past November that Johnsrud Sundby, Poltaranin and Hellner gapped the field in Sweden by around 20 seconds. Next is a classic 15km all the way back in 1996 (a regular World Cup). That was in February of 1996, in Russia, where Prokourorov, Smirnov and Daehlie (in that order) gapped the field by almost 31 seconds. That’s a larger raw interval, but as a classic race it was generally a lot slower, so the gap was smaller as a percentage of the total time.
This post is somewhat of a teaser trailer for the sorts of things we can do once we have a complete record of major international ski results stretching back to the 70’s.
A natural and possibly controversial question is whether the World Cup field has become more or less competitive over time. Intuitively, I think it’s clear that it probably has. That’s just the natural progression of any sport as it attracts more money, sponsors and participants. The skiing community as a whole simply gets better at producing fast skiers.
But this process can make it difficult to compare the results of today’s athletes to those of many years ago.
In a sort of XC skiing data fantasy world, we’d like to make direct comparisons between modern skiers and historical skiers (i.e. is Petter Northug faster than Gunde Svan?). The only real way to answer that question would involve time travel. We can, however, make relative comparisons about the entire field. So we can ask the following: Is the average 30th place finisher on today’s World Cup closer to or further behind the winner than the average 30th place finisher in 1984?
To do this I grabbed some preliminary data from my big data entry project. To keep the comparison and fair (and simple) as possible, we’re only going to look at men’s interval start classic races. (I think it’s pretty obvious that skating comparisons are going to be problematic.)
I happened to have all the results for World Cup races from the 1982-1983 and 1983-1984 seasons, so those races will serve as our “historical” data set. I’m assuming that all these races were classic races, which isn’t technically correct, if I have my history right. At least a few of these races had experimental “skating zones” where people were allowed to skate for a few hundred meters at a time. Personally, I think that’s a small enough deviation from “classic skiing” that for these purposes, we needn’t worry.
Next, we’ll take a roughly equivalent number of modern men’s interval start classic races. The result is around twenty historical races and twenty modern ones (from across the last several seasons, since classic interval start races are more spread out in the schedule).
The following graph shows the average FIS points (calculated using modern rules for all races) for both groups versus finishing place:
Now, World Cup point rules have changed as well. Back in the day, only the top twenty scored points, and the point scale differed. Still, we can make some sensible comparisons for the average 10th, 20th, etc. place finishers here.
For interval start races, FIS points are essentially just percent back times 800. This means that the average male 30th place finisher in the early 80’s was ~2.5% further behind the winner than today’s average male 30th place finisher. Two and a half percent! That’s probably almost a minute in a 15km and just over two minutes in a 30km.
Obviously, the point here isn’t that the skiers from back in the day were slow. Remember, we can’t say things like that because that would be a direct comparison. It’s just that when the sport was younger, there were fewer people able to ski close to the winner.
The way I like to think about this is to compare the World Cup circuit to a game of musical chairs. This entails reading the above graph “backwards”. Let’s start with a 30 FIS point World Cup result. If we move across horizontally from that spot on the y axis, we see that there were typically around 15 skiers in the early 80’s who were capable of finishing that close to the leader. Continuing across the graph, we can see that that number has increased to around 25 now. So you could think of that as adding 10 people to a game of musical chairs that started with 15 people and 15 chairs.
I was interested (rather than offended) to read about Noah Hoffman’s pacing strategies in Sunday’s classic WC race. I have a limited supply of data on split times (what I do have is thanks to Jan over at worldofxc.com, though) so the following data is definitely incomplete.
Hoffman seemed determined to not start too fast, something that apparently he does quite often. Since pacing interval start races is so much different than mass start or pursuits, we’ll only look at his splits for interval start races. I only have split times from a total of eight WC-level interval start races for him (of varying lengths). Here’s a simple graph showing them all together, with Sunday’s race highlighted with the black dashed line:
This is a very crude representation of split times, where I’ve simply plotted how fast Hoffman skied each timed section compared to the field. So, for example, the y-axis means he had the 20th fastest, 40th fastest, etc. split time on that section.
In order to compare races of different length I’ve converted the x-axis from raw kilometers to a percentage of the total race distance. (This may be dubious, since pacing strategies will be markedly different in a 15k versus a 30k. However, these data consist of two 10k’s, five 15k’s and only one 30k, so I think we’re on fairly safe ground.)
Certainly Noah’s first split was slower than his subsequent splits on Sunday. And it was the 3rd slowest initial split of the eight I have. But it seems to me like he proceeded to ski the rest of the race fairly consistently, rather than gradually accelerating. At least, until he faded a bit on the last section.
This is in contrast to several of the other lines here that begin with fairly quick initial splits, but by mid-race he’s clocking only ~60th fastest time on each section or so. So whatever he did seemed to work.
I should say that I’m fairly cautious about my ability to analyze split times. I’m sure the coaches are keeping more detailed data on this sort of thing than I have access to. But it’s interesting, nonetheless.
This topic is going to be somewhat more technical than usual. It involves some inside baseball, to mix sports metaphors, so if the nitty gritty details of FIS point calculations don’t strike you as an exciting page turner, you’ve been warned! However, if you stick with me, you’ll learn how brutally stupid FIS’s F-factor adjustments actually are. Yes, I said brutally stupid.